Preparation of rare earth permanent magnet material

Abstract

The present invention provides a method for preparing a rare earth permanent magnet material. The preparation method of the present invention comprises atomizing spray process and infiltrating process, wherein the atomizing-sprayed sintered rare earth magnet is placed in a closed container before infiltrating. Through the atomizing spray process a solution containing a heavy rare earth element is coated on the surface of a sintered R1-Fe(Co)—B-A-X-M rare earth magnet, and after baking, heat treatment is performed to infiltrate the sprayed heavy rare earth element to the grain boundary phase of the sintered rare earth magnet. This method decreases the amount of a heavy rare earth element used, increases the coercive force of magnets with a little decrease of remanence, decreases the remanence temperature coefficient and coercive force temperature coefficient of the magnet, and improves resistance of the magnet against demagnetization at a high temperature.

What is claimed is: 
     
       1. A method for preparing a rare earth permanent magnet material, comprising steps as follows:
 S2) atomizing spray step: placing a sintered rare earth magnet in an atomizing spray device, wherein the atomizing spray device comprises a solution tank, an ultrasonic vibrator, an atomizing nozzle, and a recovery tank; storing a solution containing an element of R2 into the solution tank; mixing the solution containing the element of R2 homogeneously by the ultrasonic vibrator; atomizing the solution containing the element of R2; spraying the atomized solution containing the element of R2 on a sintered rare earth magnet through the atomizing nozzle while the remaining atomized solution falls into the recovery tank; and baking the sintered rare earth magnet after spraying; and 
 S3) infiltrating step: placing the sintered rare earth magnet obtained from the atomizing spray step S2) in a stainless steel closed container, placing the stainless steel closed container in a vacuum infiltrating furnace, evacuating the vacuum infiltrating furnace to an absolute vacuum degree of lower or equal to 0.01 Pa, starting to heat the vacuum infiltrating furnace to 700-850° C. and keeping the temperature for 0.5-5 hours with the aim to remove the oxidation layer on a surface of the sintered rare earth magnet; and then adjusting the temperature to 900-950° C. and keeping the temperature for 1-8 hours; 
 wherein the sintered rare earth magnet is R1-Fe(Co)—B-A-X-M based rare earth magnet, 
 wherein R1 is one or more elements selected from Nd, Pr, La, Ce, Tb, Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm, Yb, Lu, Y or Sc; 
 B represents Boron element; 
 A is one or more elements selected from H, Li, Na, K, Be, Sr, Ba, Ag, Zn, N, F, Se, Te, Pb or Ga; 
 X is one or more elements selected from S, C, P or Cu; 
 M is one or more elements selected from Ti, Ni, Bi, V, Nb, Ta, Cr, Mo, W, Mn, Al, Sb, Ge, Sn, Zr, Hf or Si; and 
 R2 is one or more elements selected from Tb, Dy, Ho or Gd. 
 
     
     
       2. The preparation method according to  claim 1 , characterized in that in the atomizing spray step S2), the solution containing the element of R2 is formed by dispersing a R2 element-containing substance in an organic solvent with 0.3-0.8 g of R2 element-containing substance per milliliter of organic solvent. 
     
     
       3. The preparation method according to  claim 2 , characterized in that in the atomizing spray step S2), the R2 element-containing substance is at least one selected from a fluoride, an oxide or an oxyfluoride of the R2 element. 
     
     
       4. The preparation method according to  claim 2 , characterized in that in the atomizing spray step S2), the average particle size of the R2 element-containing substance is smaller than 3 μm. 
     
     
       5. The preparation method according to  claim 2 , characterized in that in the atomizing spray step S2), the organic solvent is at least one selected from aliphatic hydrocarbons, alicyclic hydrocarbons, alcohols or ketones. 
     
     
       6. The preparation method according to  claim 1 , characterized in that in the atomizing spray step S2), the baking temperature is 50-200° C.; and the baking time is 0.5-5 hours. 
     
     
       7. A method for preparing a rare earth permanent magnet material, comprising steps as follows:
 S1) magnet preparation step: preparing a sintered rare earth magnet; 
 S2) atomizing spray step: placing the sintered rare earth magnet in an atomizing spray device, wherein the atomizing spray device comprises a solution tank, an ultrasonic vibrator, an atomizing nozzle, and a recovery tank; storing a solution containing an element of R2 into the solution tank; mixing the solution containing the element of R2 homogeneously by the ultrasonic vibrator; atomizing the solution containing the element of R2; spraying the atomized solution containing the element of R2 on the sintered rare earth magnet through the atomizing nozzle while the remaining atomized solution falls into the recovery tank; and baking the sintered rare earth magnet after spraying; and 
 S3) infiltrating step: placing the sintered rare earth magnet obtained from the atomizing spray step S2) in a stainless steel closed container, placing the stainless steel closed container in a vacuum infiltrating furnace, evacuating the vacuum infiltrating furnace to an absolute vacuum degree of lower or equal to 0.01 Pa, starting to heat the vacuum infiltrating furnace to 700-850° C. and keeping the temperature for 0.5-5 hours with the aim to remove the oxidation layer on a surface of the sintered rare earth magnet; and then adjusting the temperature to 900-950° C. and keeping the temperature for 1-8 hours; 
 wherein the sintered rare earth magnet is R1-Fe(Co)—B-A-X-M based rare earth magnet, 
 wherein R1 is one or more elements selected from Nd, Pr, La, Ce, Tb, Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm, Yb, Lu, Y or Sc; 
 B represents Boron element; 
 A is one or more elements selected from H, Li, Na, K, Be, Sr, Ba, Ag, Zn, N, F, Se, Te, Pb or Ga; 
 X is one or more elements selected from S, C, P or Cu; 
 M is one or more elements selected from Ti, Ni, Bi, V, Nb, Ta, Cr, Mo, W, Mn, Al, Sb, Ge, Sn, Zr, Hf or Si; and 
 R2 is one or more elements selected from Tb, Dy, Ho or Gd; 
 S4) aging treatment step: the aging treatment is carried out on the sintered rare earth magnet obtained from the infiltrating step S3). 
 
     
     
       8. The preparation method according to  claim 7 , characterized in that the magnet preparation step S1) comprising steps as follows:
 S1-1) smelting step: smelting a raw rare earth magnet material so that the smelted raw rare earth magnet material forms a master alloy; 
 S1-2) powdering step: crushing the master alloy from the smelting step S1-1) into magnetic powder; 
 S1-3) shaping step: pressing the magnetic powder obtained from the powdering step S1-2) into a green body for sintering under the actions of an alignment magnetic field; and 
 S1-4) sintering step: sintering the green body obtained from the shaping step S1-3) into the sintered rare earth magnet. 
 
     
     
       9. The preparation method according to  claim 7 , characterized in that in the aging treatment step S4), the aging treatment temperature is 300-900° C.; and the aging treatment time is 0.5-10 hours.